12/15-lipoxygenase, Insulin-like Growth Factor-1 and Atherosclerosis

描述(申请人提供)：动脉粥样硬化是大多数心血管疾病相关死亡的主要潜在原因，非常需要开发针对总体疾病负担的创新疗法，并减少与斑块不稳定相关的急性血管事件。动脉粥样硬化是一种以巨噬细胞和巨噬细胞源性泡沫细胞为主的炎症性疾病。最近的研究结果表明，胰岛素样生长因子-1(IGF-1)减轻了APOE-/-小鼠的动脉粥样硬化负担，增加了斑块的稳定性，这些作用与减少斑块、巨噬细胞和脂质水平以及减少泡沫细胞有关。然而，IGF-1发挥血管保护作用的机制尚不清楚。这个探索性项目的目标是确定IGF-1改变巨噬细胞脂质摄取和减少动脉粥样硬化负担的机制。我的初步数据显示，IGF-1下调了APOE-/-小鼠和培养的巨噬细胞中12/15-脂氧合酶(12/15-LOX)的表达。后者的作用与减少细胞介导的脂质氧化和减少脂质摄取有关。12/15-LOX介导低密度脂蛋白转化为氧化型低密度脂蛋白，并通过此机制促进巨噬细胞的脂质摄取，促进泡沫细胞的形成。我将重点研究IGF-1诱导巨噬细胞12/15-LOX调控的转录机制，并确定IGF-1下调12/15-LOX的重要性以及巨噬细胞12/15-LOX在抗动脉粥样硬化中的具体作用。中心假设是IGF-1通过减少STAT-6转录因子的表达和/或活性来下调巨噬细胞中12/15-LOX的表达。这种对巨噬细胞12/15-LOX的抑制对于IGF-1诱导的动脉粥样硬化斑块负荷的减少至关重要。目的：1.研究IGF-1诱导巨噬细胞12/15-LOX下调的转录机制。具体目的2.研究12/15-LOX下调是否介导IGF-1诱导的动脉粥样硬化斑块负荷减少。预期结果：我预计IGF-1诱导的对STAT-6的抑制将下调巨噬细胞12/15-LOX，这一机制将介导巨噬细胞脂质摄取减少。我希望证明巨噬细胞特异性的12/15-LOX是IGF-1诱导的APOE-/-小鼠抗动脉粥样硬化效应的关键介质。总体而言，这些发现将确立12/15-LOX作为IGF-1诱导的体外抑制巨噬细胞脂质摄取和IGF-1诱导的APOE/-小鼠动脉粥样硬化保护的关键成分的作用。R21的预期结果将作为未来全面(R01)提案的必要实验支持，重点研究IGF-1的细胞靶向效应。此外，我预计，识别调控12/15-LOX表达的分子机制将为治疗干预提供新的靶点。

DESCRIPTION (provided by applicant): Atherosclerosis is the principal underlying cause of most cardiovascular disease-related deaths and there is a great need to develop innovative therapies targeting overall disease burden and to decrease acute vascular events related to plaque instability. Atherosclerosis is an inflammatory disease in which macrophages and macrophage-derived foam cells play a pre-dominant role. Recent findings indicate that insulin-like growth factor-1 (IGF-1) reduces atherosclerotic burden and increases features of plaque stability in Apoe-/- mice and these effects correlate with reduced plaque macrophages and lipid levels and decreased foam cells. However, mechanisms whereby IGF-1 exerts vasculoprotective effects are unclear. The goal of this exploratory project is to determine mechanism whereby IGF-1 alters lipid uptake in macrophages and reduces atherosclerotic burden. My preliminary data demonstrate that IGF-1 downregulates 12/15-lipoxygenase (12/15- LOX) expression in Apoe-/- mice and in cultured macrophages. The latter effect correlates with decreased cell- mediated lipid oxidation and reduced lipid uptake. 12/15-LOX mediates the transformation of low density lipoprotein into its oxidized form and via this mechanism 12/15-LOX enhances macrophage lipid uptake and promotes formation of foam cells. I will focus this short-term R21 exploratory proposal on studying the transcriptional mechanism of IGF-1-induced 12/15-LOX regulation in macrophages and I will also determine the importance of IGF-1 downregulation of 12/15-LOX and the specific role of macrophage 12/15-LOX for its anti-atherosclerotic effect. The central hypothesis is that IGF-1 downregulates 12/15-LOX in macrophages via reduced expression and/or activity of STAT-6 transcription factor. This suppression of macrophage 12/15-LOX is critical for IGF-1-induced reduction in atherosclerotic plaque burden. Two specific aims have been designed: Specific Aim 1. To study the transcriptional mechanism mediating IGF-1-induced downregulation of 12/15-LOX in macrophages. Specific Aim 2. To study whether 12/15-LOX downregulation mediates IGF-1-induced reduction in atherosclerotic plaque burden. Expected outcome: I anticipate that IGF-1-induced suppression of STAT-6 will downregulate macrophage 12/15-LOX and this mechanism will mediate the reduced macrophage lipid uptake. I expect to demonstrate that macrophage-specific 12/15-LOX is the critical mediator of IGF-1-induced anti-atherosclerotic effects in Apoe-/- mice. Overall, these findings will establish the role of 12/15-LOX as a key component of IGF-1-induced suppression of macrophage lipid uptake in vitro and IGF-1-induced atheroprotection in Apoe-/- mice. The anticipated results of this R21 will serve as essential experimental support for the preparation of a future full- scale (R01) proposal focusing on studying cell-targeted effects of IGF-1. In addition, I anticipate that identification of molecular mechanisms regulating 12/15-LOX expression will offer new targets for therapeutic intervention.